Phosphorodithioic zinc salt based corrosion inhibiting composition comprising an epoxy resin, acylated polyamine and filler



United States Patent 3,242,130 PHOSPHORODITHIUIC ZINC SALT BASED (30R- RUSHON INHIBITHNG COMPUSITION COMPRIS- ING AN EPOXY RESIN, ACYLATED POLYAMINE AND FILLER Le Roy G. .Iackopin, Painesville, Ohio, assignor to The ldilinhrizol Corporation, Wicklitfe, Ohio, a corporation of :0 No Drawing. Filed Nov. 9, 1961, Ser. No. 151,195 6 Claims. (Cl. 26032.8)

The present invention relates to a fluid composition adapted to provide an electrically-conductive, protective coating for metals. In a more particular sense, it relates to a fluid composition adapted to provide a weldable protective coating for ferrous metals.

It is common practice in the automotive industry to coat various ferrous undercarriage parts of passenger cars and trucks such as brackets, box-channels, panels, and braces, with a suspension of zinc dust in an organic vehicle, generally an alkyd or synthetic resin. Some manufacturers depart from this practice by coating ferrous metal stock with the zinc-filled organic vehicle before it is formed into the various parts. In any event, they all seek to provide these ferrous parts with a coating which protects them from corrosion and which, at the same time, does not impair the Weldability of the coated ferrous surface. In addition the coating must be sufiiciently hard and adherent so that it will withstand forming operations Without scoring or flaking.

'Ihe zinc-filled organic vehicles, 1i.e., zinc-filled paint-s, presently available for this purpose have not been fully satisfactory. They have afforded only limited protection against corrosion although they have been satisfactory with respect to Weldability. In an effort to improve corrosion resistance, some manufacturers have first treated the ferrous parts and/or ferrous stock from which the parts are made with an aqueous phosphating solution to form thereon an inorganic phosphate coating and thereafter applied a zinc-filled paint over the phosphate coating. Although a significant improvement in corrosion resistance is obtained by such a two-step procedure, the increased handling and processing costs have seriously limited its Widespread application.

It is an object of the present invention to provide a fluid composition which forms a protective, adherent, easily weldable coating on metal surfaces.

Another object is to provide a composition particularly adapted to prevent the corrosion of ferrous metal surfaces.

Still another object is the provision of corrosion-resistant, Weldable ferrous anticles.

According to the present invention, these and other objects are achieved by means of a fluid composition adapted to form a protective coating on metals which contains as essential ingredients (A) finely-divided zinc, (B) an epoxy resin, (C) a polyvalent metal salt of the phosphorodithioic acid prepared by the reaction of a mixture of monohydric and polyhydric alcohols with a phosphorus sulfide, and (D) an oil-soluble acylated amine prepared by the reaction of a substituted succinic compound selected from the class consisting of substituted succinic acids having the structural formula and substituted succinic anhydrides having the structural formula in which structural formulas R is a large, substantially aliphatic hydrocarbon radical having at least about carbon atoms, with more than an equivalent amount of an amine selected from the group consisting of alkylene amines and hydroxyalkyl substituted alkylene amines.

In general the fluid composition will also contain a viscosity-reducing amount of a volatile solvent and a pigment-suspending agent such as castor wax or a polyvalent metal stearate to prevent the settling and agglomeration of the Zinc dust into a hard, diificultly-dispersible precipitate.

INGREDIENT (A) Ingredient (A), the finely divided zinc, is preferably commercial powdered zinc passing 325-mesh screen according to AST M Test E 1158 T. Powdered zinc of such fineness is more readily dispersed with the other ingredients of the composition than is a coarser grade and, furthermore, shows less tendency to precipitate upon storage.

INGREDIENT (B) Ingredient (B), the epoxy resin, is any one of a number of well-known organic resins which are characterized by the presence therein of an epoxide group, i.e.,

where x is zero or a small whole number. In the last decade, a Wide variety of such resins have become available commercially.

Such resins have either a mixed aliphatic-aromatic or an exclusively non-benzenoid (i.e., aliphatic or cycloaliphatic) molecular structure.

The mixed aliphatic-aromatic epoxy resins which are preferred for the purpose of the present invention are generally prepared by the well-known reaction of a his- (hydroxyaromatic)alkane or a tetrakis-(hydroxyaromatic)alkane with a halogen-substituted aliphatic epoxide in the presence of a base such as, e.g., sodium hydroxide or potassium hydroxide. Under these conditions, hydrogen halide is first eliminated and the aliphatic epoxide group is coupled to the aromatic nucleus via an ether linkage. Then the epoxide groups condense with the hydroxyl groups to form polymeric molecules which vary in size according to the relative proportions of reactants and the reaction time. The following equations, using for purposes of illustration, epichlorohydrin and 2,2-bis-(p-hydroxyphenyl)propane as reactants, are believed to represent some of the principal reactions which occur. They do not necessarily represent all reactions, however, and it is preferred to define the epoxy resins in terms of their starting materials and average molecular Weight.

(iv) III may likewise condense with additional epichl-oro- 1O devoid of benzenoid rings, are of relatively recent origin. hydrin and 2,2-bis-(p-hydroxyphenyl)propane to form They are made commercially by oxidizing (generally by higher polymers of the postulated general structure: means of peracetic acid) various monomeric or polymeric wherein Z is an integer from 2 about 50. cyclic or acyclic olefins such as, e.'g., methylcyclohexene,

In lieu of the epichlorohydrin, one can use halogenvinylcyclohexene, alpha-methyl-vinylcyclohexene, polybusubstituted aliphatic epoxides containing 4 or more carbon tadiene, etc, which contain at least one carbonic-carbon atoms, generally 4 to carbon atoms, such as, e.g., 4- 20 multiple bond. One of such non-benzeno1d epoxy resins, chloro-1,2-epoxybutane, S-bromo 1,2 epoxypentane, 6- known by the trade designation Oxiron 20 01, is made by 'L P Y P y 7-Ch1OIO- oxidizing polybutadiene with peracetic acid. I It IS useful 2,3-epoxyoctane, 8-bromo-2,4-epoxynonane, 7,8-dichloroa the epoxy resin ingredient of a composition of the 1,2-epoxydecane, 16-bromo 1,2 epoxyhexadecane, 20- present invention. It is likewise usefulwhen blended with iodo-16-k -1,2- p Xy i n 14-Ch10f0 a mixed aliphatic-aromatic epoxy resin of the type depoxytetradecane, and the like. In general it is preferred scribed earlier. to use a chlorine substituted terminal alkylene oxide INGREDIENT (C) (terminal denoting that the epoxide group is on the end Ingredient (C), [the polyvalent metal ,Salt of a phos of the alkyl chain) and a particular preference is expressed phomdithioic acid prepared by the reaction of a mixmlm for epichlorohydrin y reason of its cheaphess: of monohydric and polyhydric alcohols withaphosphorus mercial availability, and excellence in forming P Y sulfide, is described in detail in US. Patent 2,861,907, resins useful for the Purpose of this ihvehtiohowned by the assignee of the present application. In the If desired, the halogen Substituted aliphatic ePOXide interest of not unduly lengthening the present specification, may also contain Shhstithehts Such hydroxy keto: it is intended that the entire disclosure of this patent be him), hitroso, ether, Sulfide: carhoalkoxy incorporated herein by reference. In brief, the patent Similarly, in lieu of the h h describes the reaction of a mixture of a monohydric alco- Propane, one can use his'(hydhoxyahomatic)alkahas hol and from 0.25 to 4.0 equivalents of a polyhydric alcotaining 16 or more carbon atoms, generally 16 to 30 carhol with a phosphoms sulfide, preferably P255, to form a boil moms Such as, -t h n' complex phosphorodithioic acid which is then converted P p 23-1315-(ohydhloxyplhehyl)Phopahe; 40 to a polyualent metal salt by conventional methods. hydroxyphenybbutane, 3,3 bis-(p-hydroxyphenyl)h xan The monchydric alcohols contemplated as reactants in 2 (P y yp y y p the preparation of Ingredient (C) of this invention include bis (l y yy p "(P' principally lallcanols, although alcohols such as phenethyl yp y' l his (P- Y Y'- P PY and benzyl alcohols likewise may be used. For the most P YDP P -(QP- y p )P part, however, such alkanols as ethyl, butyl, hexyl, octyl, 2 (l Y YP YD- Y YP Y decyl, dodecyl, etc, alcohols are contemplated as the and th likef desired, the his-(hydroxyammafic)alkane nronohydric alcohol reactant. A particularly preferred may contain Sub titut nt 8110b -g-, halogen, nitro, subclass of monohydric alcohols are the octyl alcohols. ether, Sulfide, harboalkOXY: In gellef it is p The polyhydric alcohol reactant may be selected from ffirrfid to use a -(P- Y YP l/D alkane Since the various dihydric, trihydric, tetrahydric, and higher Pounds of this yp are readily available from the W611- polyhydric alcohols. Illustrative examples of such polykncwn condensation of phenols with aliphatic ketones or hydpic l h l i l d h l l l, propylene l ol, aldehydes in the PmshllCe of a dehydrating agent Such as butylene glycol, glycerol, pentaerythritol, butenediol, sulfuric acid. Aparticular preferance is expressed for 2,2- butynediol, t It i contemplated lik i to employ -(P- Y YP YDP P 0011111101113 referred to in polyhydric alcohols which contain aromatic sub-stituents. the trade as Bisphenol A, by reason of its low cost and Th proportions of monohydric rand polyhydric alcocommercial availability.

hols which are to be used in the preparation of Ingredient Epoxy resins which are especially suited for the purpose (C) are governed by considerations of solubility and fluidof the present invention are prepared by the reaction of a it on the one hand, and of satisfactory film-forming bis (hydroxyphenyDalkane, preferably 2,2 bis-(19 3- properties on the other hand. It has been found that the droxyphenyl)propane with a chlorine substituted terminal use of a disproportionately large amount of polyhydric alkylene oxide, preferably epichlorohydrin, to produce a alcohol in the reaction mixture results in a product which product having an average molecular weight Within th is too insoluble and intractable to allow convenient applirange of 3 00 to 500 and preferably 350 to 400. One of cation to a metal surface. If the proportion of polyhydric such preferred epoxy resins having an average molecular alcohol used in the reaction mixture is below a certain weight of about 380 and prepared from 2,2-bis-(p-hyminimum quantity, then the resulting product, although droxyphenyDpropane and epichlorohydrin is known by sufficiently fluid and soluble in many solvents, is not a the trade designation Epon 820. A related type of satisfactory film-forming material. In view of these obepoxy resin having an average molecular weight of about servations, it has been determined that the amount of 616 and prepared from epichlorohydrin and symmetrical "0 polyhydric alcohol which can be used satisfactorily in tetrakis-(p hydroxyphenyl)ethane is available under the the preparation of Ingredient (C) is Within the range of trade designation Epon 1031. 0.25 to 4.0 equivalents per equivalent of monohydric Another general class of epoxy resins which are useful alcohol present in the reaction mass. It is particularly for the purpose of the present invention are the aliphatic preferred to employ approximately equivalent amounts of or cycloaliphatic epoxy resins. These resins, which are monohydric and polyhydric alcohol reactants. The term equivalent as used above is based upon a consideration of the number of hyd-roxyl groups in the particular alcohol reactant. Thus the equivalent weight of ethylene glycol is 31, one-halt. of the molecular Weight thereof. The equivalent weight of pentaerythritol is 34, one-fourth the molecular weight thereof.

The reaction by which phosphorodithioic acids are prepared is well-known. It involves the reaction of one mole of phosphorus pentasulfide with 4 equivalents of an alcohol or mixture of alcohols. Lesser or greater amounts of alcohol can be used, of course, but in such instances there is either incomplete reaction or an excess of the alcohol remains as a diluent in the final product.

The metal constituent of Ingredient (C) is a polyvalent metal such as, e. g., barium, calcium, strontium, magneslum, zinc, cadmium, iron, manganese, lead, tin, nickel, cobalt, chromium, beryllium, etc. The diva-lent metals are preferred, and of these zinc is particularly prefer-red. These metal salts are prepared ctrom the phosphorodithioic acid, generally by neutnalization thereof with the particular basic metal compound 01f the desired metal. Thus the preparation of a zinc phosphorodithiolate may be effected by the neutralization of the phosp horodithioic acid with zinc oxide. Similarly a barium salt may be prepared by neutralization with barium hydroxide octahydna-te. Other methods of formation of such polyvalent metal salts may be accomplished by reaction on? the phosphorodithioic acid with the free metal, or by the metathesis of a monovalent metal phosphonodithioate 'SlllOh as a sodium or potassium phosphorodithilo-atte a soluble metal salt, e.g., a chloride or nitrate, of the polyvalent metal.

Polyvalent metal phosphorodithioates disclosed in the patent and useful for the purpose of the present invention are shown in Table 1:

TABLE 1 Polyvalent metal phosphorodithioate Example No. of U S Phosphorodithioic acid preparation 2,861,907

Metal Alcohol Equiva- Moles lents P18 n-Octyl alcohol 1,2-propylenc glycol. Isooctyl alcohol.

tdiol Isooctyl alcohol 2-buty'ne-lA-diol. Isooctyl alcohol. Dipropylene glycoL- Isooctyl alcohol Dipropylene glycoL.

comm e WWW VHHWVWDWWWWHDVMWV ee Diethylene glycol. Isooctyl alcohol. Dipropylenc glycoL- Pentaerythritol. Isooctyl alcohol. Diethyleneglycol.... Isocctyl alcohol- Neopcntyl glycol.. Isooctyl alcohol 2,2-bis(4-betahydroxyethoxyphcnyl) propane. Isooetyl alcohol Diethylenc glycol. Isooctyl alcohol- Dipropylene glycoL- Isooetyl alcohol Propylene glycol. Isooctyl alcohol. Propylene glycol.

For the purpose of the present invention the zinc phosphorodithioates are preferred and a particular preference is expressed for the low-cost zinc salt of the phosphorodithioic acid prepared by the reaction of equivalent amounts of isooctyl alcohol and dipropylene glycol with 6 phosphorus pentasulfide as specifically described in Example 5 of US. Patent 2,861,907.

In some instances, zinc phosphorodithioates prepared from mixtures of monohydric and polyhydric aromatic alcohols (i.e., phenols) are also useful as Ingredient (C) of this invention. Specifically illustrative of the preparation of this type of zinc phosphorodithioate is the following:

Example C] In a flask equipped with a stirrer, 576 grams (3 moles) of heptylphenol and 114 grams (0.5 mole) of 2,2-bis- (p-hydroxyphenyl) propane are introduced and heated to C. While the whole is stirred vigorously, 222 grams (1 mole) of P 8 is added gradually over a period of 3 hours and heating is continued for an additional 3 hours. Filtration of the mass yields the desired complex phosphorodithioic acid, which is diluted with an equal weight of toluene to facilitate handling.

1376 grams of the toluene solution of the acid is mixed with 75 grams of zinc oxide and 5 grams of water. The whole is heated for 5 hours at 60-65 C. and then filtered to yield a filtrate which is a 51.2% solution of the desired zinc phosphorodithioate in toluene. It contains 2.99% of phosphorus, 6.31% of sulfur, and 3.34% of zinc.

INGREDIENT (D) Ingredient (D), the oil-soluble acylated amine, is described in detail in the copending application of W. M. Le Suer et 211., Serial No. 802, 667, filed March 30, 1959, now US. Patent 3,172,892, and owned by the assignee of the present application. In the interest of not unduly lengthening the present specification it is intended that the disclosure of the said Le Suer et a1. application, particularly the portion thereof which deals with species of acylated amines derived from the reaction of a sub stituted succinic compound with more than an equivalent amount of an ethylene amine, be considered as forming a part of the present specificatibn.

In summary, Serial No. 802,667 deals with mixing a substituted succinic compound selected from the class consisting of substituted succinic acids having the structural formula RCHC 0 OH CIIr-COOII and substituted succinic anhydrides having the structural formula RCH-C 0 0 CIILP'CO in which structural formulas R is a large, substantially aliphatic hydrocarbon radical having at least about 50 carbon atoms, with at least about one-half an equivalent amount of an ethylene amine, and heating the resulting mixture to effect acylation and remove the water formed thereby.

The size of the substituent on the succinic acid or an hydride is of importance in the preparation of Ingredient (D) because it allows the preparation of a product which satisfies the objects of this invention. It is important that this su'bstituent be large, that it have at least about 50 carbon atoms in its structure. These substituent groups are substantially aliphatic hydrocarbon radicals including both alkyl and alkenyl radicals. They are commonly derived from polyolefins such as polyethylene, polypropylene, polybutene, polyamylene, etc., although they may be derived from any substantially aliphatic hydrocarbon.

The substituted succinic acids and anhydrides which are contemplated as a reactant in the process for the prep arati-on of Ingredient (D) are readily available from the reaction of maleic anhydride with a high molecular weight olefin or a chlorinated high molecular Weight olefin. The product from such a reaction is the corresponding alkenyl succinic anhydride. The reaction involves merely heating these two reactants at a temperature of about 150 to 200 C. The reactants in each case are illustrated by the following equations:

O O CH 0 CIIzC O RCH CH CI CIICO RCH=CIICIICO O O CH0 0 CHzC 0 It will be appreciated that the reactions may not go precisely as indicated above, especially with respect to the particular carbon atom of the olefin or chloride reactant which ultimately becomes attached to the maleic acid or anhydride reactant, but other than this the equations are believed to be illustrative. Furthermore, although the product of this reaction has been indicated as being an alkenyl succinic anhydride; it is apparent that similar products can be prepared by this process in which the substituent is something other than an alkenyl group. For the purpose of the present invention this substituent should, however, be substantially aliphatic group and in most cases, of course, it will be an alkyl or alkenyl group. In some cases, however, it may well be desirable to employ a substituted succinic anhydride in which the substituent is derived from a copolymer of styrene and isobutylene, or of a substituted styrene and some other aliphatic olefin. In these cases copolyrner will be substantially aliphatic, that is, the composition of the copolymer will be predominantly aliphatic.

The most commonly used sources of the substantially aliphatic hydrocarbon substituents are the polyolefins. These are illustrated by polyethylene, polypropylene, polyisobutene, etc. A particularly preferred polyolefin for this use is polyisobutene. Thus the condensation of a polyisobutene having a molecular weight of about 750 with maleic anhydride yields an alkenyl succinic anhydride which upon further reaction with an ethylene amine produces a material which is particularly effective as Ingredient (D) of the present invention.

The substituted succinic anhydride ordinarily is reacted directly with the ethylene amine, although in some instances it may be desirable first to convert the anhydride to the acid before reaction with the ethylene amine. In other circumstances it may be desirable to prepare the substituted succinic acid by some other means and to use an acid prepared by such other means in the process. In any event, either the acid or the anhydride may be used in the preparation of Ingredient (D).

The term ethylene amine is used in a generic sense to denote a class of polyamines conforming for the most part to the structure:

in which x is an integer and R is a low molecular weight alkyl radical or hydrogen. Thus it includes, for example, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, etc. These compounds are discussed in some detail under the heading ethylene amines in Encyclopedia of Chemical Technology, Kirk and Othmer, volume 5, pages 898-905, Interscience Publishers, New York (1950). Such compounds are prepared most conveniently by the reaction of ethylene dichloride with ammonia. This process results in the production of somewhat complex mixtures of ethylene amines, including cyclic condensation products such as piperazines, and these mixtures find use in the preparation of Ingredient (D). On the other hand, quite satisfactory products may be obtained also by use of pure ethylene amines. An especially useful ethylene amine for reasons of economy as well as effectiveness is a mixture of ethylene amines prepared by the reaction of ethylene chloride and ammonia, having a composition which corresponds to that of tetraethylene pentamine. This is available in the trade under the trade name Po lyiamine H.

It has been noted that more than a chemically equivalent amount of the ethylene amine per equivalent of substituted succinic compound should be used to produce a product which is satisfactory as Ingredient (D). Amounts of the ethylene amine ranging from about 1.1 to about 8 equivalents, preferably from about 1.5 to about 4 equivalents, per equivalent of substituted succinic compound are generally used. Amounts greater than 8 equivalents of ethylene amine per equivalent of substituted succinic compound may also be used if desired, but there appears to be no advantage in the use of such large amounts of the ethylene amine reactant. The chemical equivalency of the ethylene amine reactant is based upon the nitrogen content, i.e., one having 4 nitrogens per molecule has 4 equivalents per mole.

In the preparation of Ingredient (D), the ethylene amine and the substituted succinic compound are mixed and heated at a temperature within the range of about C. to about 200 C., preferably C. to C., until most or all of the water of reaction has been removed. Thus a useful method of carrying out this step is to add some toluene to the reaction mixture and remove the water of reaction by azeotropic distillation.

It has been found that in lieu of the ethylene amine reactant, one can use for the purpose of the present invention any alkylene amine or hydroxyalkyl substituted alkylene amine reactant conforming for the most part to the structure in which n is an integer, A is hydrogen, a hydrocarbon radical, or a hydroxyalkyl radical, and Q is a divalent aliphatic radical containing at least 2 carbon atoms. The A substituents in the above formula can also be considered as forming a divalent alkylene radical, in which instance a cyclic structure results. Q is generally an alkylene radical such as ethylene, trimethylene, tetramethylene, etc., although in certain instances it may be an aliphatic radical which contains ether or sulfide substituents such as, e.g., an -alkylene-O-alkyleneor -alkylene- S-alkylene-radical.

Specific examples of such amine reactants are trimethylene diamine, di-(trimethylene)triamine, tris-(trimethyl ene)tetramine, tri-(hexamethylene)tetramine, decamethylene diamine, N-octyl trimethylene diamine, N,N-dioctyl trimethylene diamine, N-(2-hydroxyethyl)ethylene diamine, piperazine, 1-(2-aminopropyl)piperazine, 1,4- bis- 2-aminoethyl piperazine, 1- Z-hydroxyethyl piperazine, di-(hydroxypropyl-substituted)tetraethylene pentamine, N-(3-hydroxypropyl)tetramethylene diamine, pyrimidine, Z-methyI-imidazoline, and 1,3-bis-(2-aminoethyl)imidazoline.

Specific examples of acylated amines which are disclosed in detail in Serial No. 802,667 and which are useful as Ingredient (D) are shown in Table 2:

Additional examples of acylated amines useful as ingredient (D) are as follows:

Example D] A polyisobutene-substituted succinic anhydride. is prepared by the reaction of a chlorinated polyisobutene (ca. 4% chlorine content) with maleic anhydride at 200 C. The polyisobutene has an average molecular weight of 850 and the resulting alkenyl succinic anhydride is found to have an equivalent weight of about 515. A mixture of 3 parts of triethylene tetramine and 1 part of diethylene triamine, by weight, in the amount of 279 grams (7.76 equivalents based on nitrogen) is added to a solution of 1000 grams (1.94 equivalents) of the alkenyl succinic anhydride in 200 grams of toluene over a period of 4 minutes at 57-88 C. After the initial exothermic reaction subsides, the whole is heated for hours at 155 C. The water of reaction is collected in a side arm water trap and amounts to about 26 grams. The reaction mass is then stripped of solvent by heating at 160 C./5 mm. Hg until distillation ceases. The residue is an acylated amine having a nitrogen content of 7.54%.

Example D2 In a manner like that described in Example D-l, 249 grams (4 equivalents based on nitrogen) of bis-(3-aminopropyl)arnine is mixed with a solution in 266 grams of toluene of 920 grams (1.33 equivalents) of a polyisobutene-substituted anhydride having an equivalent weight of about 690. The whole is heated for 6 hours under reflux and then heated to 220 C./3 mm. Hg to remove the solvent. The residue is an acylated amine having a nitrogen content of 4.0%.

Example D-3 In a manner like that described in Example Dl, 333 grams (3.78 equivalents based on nitrogen) of bis-(3- aminopropyl)ether of ethylene glycol is reacted with 1000 grams (1.89 equivalents) of a polyisobutene substituted succinic anhydride having an equivalent weight of about 530, using 300 grams of xylene as a reaction solvent. Upon removal of the xylene solvent the acylated amine remains as the residue. It contains 4% of nitrogen.

Example D4 In a manner like that described in Example D-l, 418 grams (3.78 equivalents based on nitrogen) of bis-(3- aminopropyl)ether of diethylene glycol is reacted with 1000 grams (1.89 equivalents) of a polyisobutene substituted succinic anhydride having an equivalent weight of about 530, using 300 grams of toluene as a reaction solvent. Upon removal of the toluene solvent, the acylated amine remains as the residue. It contains 3.8% nitrogen.

Example D5 In a manner like that described in Example D1, 194 grams (3.74 equivalents based on nitrogen) of N-(2- aminoethyl)ethanolamine is reacted with 1000 grams (1.87 equivalents) of a polyisobutene substituted succinic anhydride having an equivalent weight of about 535, using 786 grams of toluene as a reaction solvent. Upon removal of the toluene solvent, the acylated amine remains as the residue. It contains 4.3% nitrogen.

Each of the Ingredients (A), (B), (C), and (D) are essential in preparing the fluid compositions of the present invention. In addition to these characterizing ingredients it is generally desirable to have present a small proportion of a pigment-suspending agent such as castor wax or a polyvalent metal stearate such as, e.g., zinc stearate, cadmium stearate, or aluminum stearate, to prevent the settling of Ingredient (A), the Zinc dust, from the other ingredients of the coating composition. In most instances it is also desirable to dilute one or more of the characterizing ingredients or mixtures of two or more of such ingredients with a viscosity-reducing amount of a volatile solvent so as to facilitate the application of the coating composition to metal surfaces. Solvents useful for this purpose include those which are commonly employed in the paint and lacquer industry such as, e.g., petroleum hydrocarbon solvents; alcohols such as, e.g., methyl, ethyl, propyl, butyl, and amyl alcohols; ketones such as, e.g., acetone, diethyl ketone, methyl isobutyl ketone, methyl ethyl ketone, etc.; the lower chlorinated alkanes such as, e.g., ethylene dichloride, 1,2-dichloropropane, butyl chloride, etc.; aromatic hydrocarbons such as, e.g., benzene, toluene, xylene, mesitylene, etc.; and aliphatic ether such as, e.g., diisopropyl ether, diisobutyl ether, and the like. In certain instances it is desirable to use mixtures of two or more solvents.

Although the proportions of the several ingredients are not particularly critical, best results from the standpoint of economy, ease of application, and weldability of the coated metal surface are obtained when one uses a composition prepared from a mixture of from about to about 200 parts preferably from about to about parts, of Ingredient (A), the zinc dust; from about 10 to about 30 parts, preferably from about 14 to about 25 parts, of Ingredient (B), the epoxy resin; from about 4 to about 16 parts, preferably from about 6 to about 10 parts, of Ingredient (C), the complex polyvalent metal phosphorodithioate; and from about 5 to about 15 parts, preferably from about 8 to about 12 parts, of Ingredient (D), the oil-soluble acylated amine; all parts being by weight. To this mixture there may be added, optionally, a small amount, generally from about 1 to about 3 or 4 parts, of a pigment-suspending agent and at least about 25 parts, preferably from about 30 to about 70 parts, of a viscosity-reducing solvent. The use of a pigment-suspending agent, although not absolutely essential, is required if settling of the Zinc dust is to be avoided. In the absence of this agent, the composition must be stirred at frequent intervals after preparation and during use. Thus, for obvious practical reasons, it is highly desirable to include a pigment-suspending agent in the compositions of this invention.

The order of mixing the ingredients of the composition is not critical when the composition is prepared for immediate use. It is generally most convenient, however, to mill the pigment-suspending agent, if one is to be used, in the solvent-diluted epoxy resin Ingredient (B) by means of a ball mill or other conventional paint-dispersing equipment. This mixture is then removed to another vessel equipped with means for stirring an Ingredients (C) and (D) are added and stirred well. A small proportion of solvent, either added directly to the vessel contents or present in Ingredients (C) and/ or (D), serves to facilitate the mixing operation. After the mixture has been stirred for a suflicient time to become homogeneous, the zinc dust is added slowly While the whole is stirred vigorously. The consistency of the mass is then adjusted by the addition, if required, of a further amount of solvent so as to yield a composition which has *a viscosity well-suited for the particular method by which it is to be applied to a metal surface. The application to a metal surface may be made by any one of the methods commonly used in the paint industry such as, e.g., dipping, brushing, roller-coating, or spraying.

If the composition is not to be used until quite some time after preparation, for example, if it is to be stored for a period longer than about one month before use, then Ingredients (C) and (D) should be stored apart from the other ingredients of the composition. Tests have shown that a complete composition has a tendency to set to an irreversible gel after having been stored for about one month in a sealed can. This gelation can be avoided, as indicated, by storing Ingredients (C) and (D) separately or admixed with each other and then adding them to the remaining ingredients shortly before the complete composition is to be used. Of course, in instances where the composition is to be used within, say, 3 weeks, no such storage precautions are necessary.

Although any of the various Ingredients (A) through (D) described earlier may be used in compounding the composition of the present invention, certain ingredients and combinations thereof are preferred for reasons of their commercial availability and economy. Thus, for example, a very useful and economical group of compositions of this invention contain as essential ingredients (A) from about 125 to about 200 parts of powdered zinc, (B) from about to about 30 parts of an epoxy resin of 300-500 average molecular weight prepared by the reaction of a bis-(p-hydroxyphenyl)alkane with a chlorine-substituted terminal alkylene oxide, (C) from about 4 to about 16 parts of a zinc salt of the phosphorodithioic acid prepared by the reaction of a mixture of a monohydric alcohol and from 0.25 to 4.0 equivalents of a polyhydric alcohol with phosphorus pentasulfide, (D) from about 5 to parts of an oilsoluble acylated amine prepared by the reaction of a polyisobutene-substituted succinic anhydride with from about 1.5 to about 4 equivalents of an ethylene amine, and (E) at least about parts of a volatile solvent.

A preferred sub-class of compositions in the above group include those compositions which contain as essential ingredients (A) from about 150 to about 175 parts of powdered zinc passing 325-mesh screen, (B) from about 14 to about 25 parts of an epoxy resin of 350-400 average molecular weight prepared by the reaction of 2,2-bis-(p-hydroxyphenyl) propane with epichlorohydrin, (C) from about 6 to about 10 parts of a zinc salt of a phosphorodithioic acid prepared by the reaction of a mixture of about equivalent amounts of isooctyl alcohol and dipropylene glycol with phosphorus pentasulfide, (D) from about 8 to about 12 parts of an oil-soluble acylated amine prepared by the reaction of a polyisobutene-substituted succinic anhydride where in the polyisobutene has an average molecular weight of about 750 with about 4 equivalents of a mixture of diethylene triamine and triethylene tetramine, and (E) from about and about 70 parts of a volatile solvent consisting of a mixture of aromatic petroleum spirits and methyl isobutyl ketone.

The aromatic petroleum spirits useful in preparing the compositions of the present invention are available from various pertoleum refiners. They generally boil in the range from about 300 to about 400 F. and have a Kauributanol value of from about 50 to about 125. An economical, commercially available mixture of aromatic petroleum spirits boils in the range 316349 F. and has a Kauri-butanol value of about 91.

Specific illustrations of the preparation of compositions of this invention are as follows:

Example I 1.63 grams of a commercial grade of castor wax known as Thixcin R is dispersed in 19.34 grams of; an epoxy resin prepared from 2,2-bis-(p-hydroxyphenyl) propane and epichlorohydrin and having an average molecular Weight of about 380 (available commercially under the trade designation Epon 820) and 19.34 grams of a solvent (solvent X) consisting of a mixture of 2 parts of methyl isobutyl ketone and 1 part of commercial aromatic petroleum spirits boiling in the range of 316349 F. and having a Kauri-butanol value of 91. After the castor wax has been thoroughly dispersed in the epoxy resin solvent solution (15 minutes is normally required when a conventional paint-shaking machine is used), the whole is transferred to a vessel equipped with a propellertype stirring device. 10 grams of an solution in solvent X of a complex zinc phosphorodithioate according to Example 5 of US. Patent 2,861,907 and 19.32 grams of a 50% solution in solvent X of the acylated amine of Example D-l are added to the vessel and the whole is stirred vigorously until the ingredients form a homogeneous mass. Then, while stirring is continued, 163 grams of powdered Zinc passing 325-mesh screen is added gradually to the vessel over a. period of about 10 minutes. When the zinc powder is thoroughly dispersed in the liquid ingredients, the composition is ready for packaging or use.

Example I] In a manner like that described in Example I the following ingredients are blended toform a composition of the invention:

0.75 grams of Thixcin R dissolved in 87.75 grams of solvent X 115.5 grams of Epon 820 dissolved in 115.5 grams of solvent X 15.62 grams of the zinc phosphorodithioate-toluene product of Example C-1 115.5 grams of a 50% solution in solvent X of the acylated amine of Example D-l 978 grams of powdered zinc passing 325-mesh screen Additional examples of compositions of the invention are shown in Table 3:

TABLE 3 Pigment suspending Epoxy resin PMP 1 Aeylated amine Solvent Zn dust, agent Ex. N0. gins.

Identity Gms. Identity Gms. A B Identity Gms. Identity Gms.

Al stcarate 3 Epon 1031 25 1 5 Ex. D-2 11 Methylethyl ketone 35 Diisopropyl etl1er 30 190 Zn stearatc. 4 Epon 820 15 7 10 Ex. D-l G Aroi nattic petroleum 30 spin 5. Diethyl ketone 20 Castor \vax 1. 5 Ouron 2001 so 12 15 Ex. D-3 14 gg i g i 15 Castor Wax 1.5 Epon 820 8 l e y 150 my 15 Cd stearate 1.5 Epon 1031 6 17 12 8 l k to 40 Oxiron 2001- 15 200 Castor wax... s {Epon 820 15 15 10 Ex. D4 10 45 140 {Castor wax... 2 Oxiron 2001- 20 18 8 {Ex 5 of S01. 7 {Diisobutyl ketone 40 Zn stearate- 2 10 No. 802,667. Mesitylene 1. 20 16 0 t 2 5 23 9 10 3 12 {fr t il l io t i m .1 as or wax e y iso u y 60 Epon 1031"... 5 ketone.

1 PMP=Polyvalent metal phosphorodithioate. 2 Boiling range, BUS-349 F. and Kauri-butanol value of 91.

C01. A=Ex. No. in 11.8. Patent 2,861,907. 001. B=grarns employed.

The compositions of this invention are generally applied to the metal surface to be protected in an amount sufficient to yield a dried film thickness of from about 0.5 to about mils and preferably from about 1 to about 3 mils. After application to the metal surface, the composition may be dried by any one of the various methods commonly employed in the paint and lacquer field such as, e.g., airdrying at ambient temperature, drying in a current of hot air, baking in an oven, or baking under a bank of infrared lamps. Best results from the standpoint of good adherence, film hardness, and corrosion protection are obtained with the compositions of this invention when a film thereof is dried by a baking procedure. Oven-braking procedures call for exposure of the coated metal surface to temperature in the range of 250-450 F. for a period ranging from about 1 minute to about 1 hour. The lower baking temperatures generally require longer periods of time than the higher baking temperatures; for example, typical procedures call for baking at 400 F. for 2 minutes, or minutes at 360 F. or 45 minutes at 250 F.

In most instances the compositions of this invention Will be applied directly to the bare metal surface to be protected. In certain applications however, where superior corrosion resistance is sought, the metal may be pretreated with a metal passivating solution such as, e.g., a dilute chromic acid solution, or an aqueous phosphating solution such as, e.g., aqueous acidic zinc di-hydrogen phosphate, aqueous acidic manganese dihydrogen phosphate, and the like. Such metal passivating or phosphating techniques are well-known and are described for example, in US. Patents 1,206,075, 1,247,668, 1,305,331, 1,485,025, 1,610,362, 1,980,518, 2,001,754, 2,901,385, 2,846,342, 2,868,682, 2,901,437, and 2,876,150. A very useful and effective class of aqueous phosphating solutions containing as essential ingredients zinc ion, phophate ion, nitrate ion, and calcium ion are described in US. applica tion Serial No. 373,449, filed August 5, 1953, now US. Patent 3,090,709, by John A. Henricks, and owned by the assignee of the present application.

In addition to pretreatment of the metal surface, it may also be desirable in certain instances, particularly Where decorative effects are sought, to top-coat the dried film of .a composition of this invention With a paint, paint primer, lacquer, or enamel. The compositions of this in vention serve as an excellent base for such top-coats in that they inhibit the deterioration of the underlying base metal and thereby remove the principal cause of blistering, flaking, and other forms of loss of coating adhesion. The above discussion regarding pretreatment of the metal surface and top-coating of the dried film of the compositions of this invention is not to be construed as indicating that such pretreatments or post-treatments are at all re- A number of tests were carried out to determine the eflicacy of the present compositions, including tests to measure film hardness, adhesion, and corrosion prevention.

In all of the tests, 4-inch x 8-inch panels of clean, solvent-degreased, 20-gauge SAE 1020 cold-rolled steel prepared according to ASTM procedure D 609-52 were used to receive films of the coating compositions of this invention. The compositions were brushed on the steel panel and dried in the indicated manner to provide a film having a thickness of 1.5i0.2 mils. The prepared panels were then subjected to the tests described below, the results of which are given in Table IV.

Sward film hardness.-This test is carried out using a Model C Sward Rocker Hardness apparatus manufactured by Gardner Laboratory, Inc. In this test a dual metal wheel, weighted unequally and having a bladed periphery, is placed in contact with the surface to be tested at F. The Wheel is set in motion and the number of swings (i.e., one-half the number of oscillations) of predetermined magnitude are counted. The harder the surface, the greater the number of swings. Conversely, the softer or the tackier the surface, the fewer the number of swings. Thus, the rating expressed in swings is a measure of the relative hardness of the surface under test.

Conical mandrel adhesion.The apparatus employed in this test is described in AST M procedure D 52241. In this test a 4-inch x 8'inch coated panel is placed in contact with a steel cone of fixed size and shape and then bent 180 along its 4-inch dimension. The panel is removed from the bending apparatus and adhesive cellophane tape is applied to the coating on the bent portion of the panel. 'The tape is then rapidly removed and the percent of coating still adhering to the panel is estimated and reported as percent adhesion.

Salt fog corrosion-The apparatus used for this test is described in ASTM procedure D 117-57T. It consists of a chamber in which a mist or fog of 5 percent aqueous sodium chloride is maintained in contact with test panels for a predetermined time at i2 F.

In the 120-hours test, the coating on the panel is pierced with a pointed instrument to yield a vertical scribe beginning one inch from the top of the panel and ending one inch from the bottom thereof. The panel is then placed in a chamber for 120 hours and removed for inspection. The creep rating is the average loss of coating from each side of the scribe expressed as an integer which represents the number of thirty-seconds of an inch. The panel is also visually inspected for rust and the amount thereof is reported as percent of area rusted.

In the 25 0-hour test, an unscribed, coated panel is placed in the chamber for 250 hours then removed for inspection. The amount of rust is reported as percent of area rusted.

TABLE 4 Sward film hardness Conical mandrel adhesion Salt fog corrosion! Composition of Ex. Remarks N 0. Panel Panel Percent Panel Test, Creep Percent prcpara- Rating Remarks prepai a adhesion Remarks preparahours rating of area tion 1 tion tion rusted 2 7 Very good. A Excellent 0 gi g figf Very good; few 5 Good. 7 A 100 hairline cracks. 250 l 3 i: 5 Do. 6 Good v B 120 0 Very good. llligcocdllent: }A 100 Excellent 250 1 0 Excellent.

1 A=Film baked in an oven 2 minutes at 400 F.

B=Film baked in an oven 2 minutes at 400 F and then 15 minutes at 360 F.

C=Film air-dried for 15 hours at room temperature.

2 Inspection for rust does not include the so-called white corrosion which results irom the conversion of the zinc powder to zinc salts and which is expected in zinc-filled paints that protect ferrous surfaces by the sacrificial consumption of Z1110 metal.

quired for adequate protection of metal surfaces. It has been offered merely to point out the versatility of the present compositions in adhering well to modified metal surfaces and in providing an excellent paint base in applications where a top-coat must be applied.

What is claimed is:

1. A fluid composition adapted to form a protective coating on metals which contains as essential ingredients (A) finely divided zinc, (B) an epoxy resin selected from the group consisting of aliphatic-aromatic, aliphatic, and

Y 15 cycloaliphatic epoxy resins, (C) a polyvalent metal salt of the phosphorodithioic acid prepared by the reaction of a mixture of monohydric and polyhydric alcohols with a phosphorus sulfide, said polyvalent metal being selected from the group consisting of barium, calcium, strontium, magnesium, zinc, cadmium, iron, manganese, lead, tin, nickel, cob-alt, chromium, and beryllium, and (D) an oilsoluble acylated amine prepared by mixing and heating at a temperature of from about 80 C. to about 200 C., a substituted succinic compound selected from the class consisting of substituted succinic acids having the structural formula and substituted s-uccinic anhydrides having the structural formula CHrC O in which structural formulas R is a large, substantially aliphatic hydrocarbon radical having at least about 0 carbon atoms, with more than an equivalent amount of amine of the structure in which n is an integer, A is selected from the group consisting of hydrogen, a hydrocarbon radical, and a hydroxyalkyl radical, and Q is a divalent aliphatic radical containing at least 2 carbon atoms.

2. A composition in accordance with claim 1 further characterized in that the epoxy resin of (B) is prepared by the reaction of a bis (hydroxyaromatic) alkane with a halogen-substituted aliphatic epoxide.

3. A composition in accordance with claim 1 further characterized in that the polyvalent metal salt of (C) is a zinc salt.

4. A composition in accordance with claim 1 further characterized in that the acylated amine of (D) is prepared by the reaction of an olefin polymer-substituted succinic anhydride with more than an equivalent amount of an amine of the structure in which n is an integer, A is selected from the group consisting of hydrogen, a hydrocarbon radical, and a hydroxyalkyl radical, and Q is a divalent aliphatic radical containing at least two carbon atoms.

5. A fluid composition adapted to form a protective coating on metals which contain as essential ingredients (A) from about to about 200 parts of powdered Zinc, (B) from about 10 to about 30 parts of an epoxy resin of 300500 average molecular weight prepared by the reaction of a bis-(p-hydroxyphenyl) alkane with a chlorine-substituted terminal alkylene oxide, (C) from about 4 to about 16 parts of a zinc salt of the phosphorodithioic acid prepared by the reaction of a mixture of a monohydric alcohol and from 0.25 to 4.0 equivalents of a polyhydric alcohol with phosphorus pentasulfide, (D) from about 5 to about 15 parts of an oil-soluble acylated amine prepared by mixing and heating at a temperature of from about 80 C. to about 200 C., a polyisobutene-substituted succinic anhydride with from about 1.5 to about 4 equivalents of an ethylene amine, and (E) at least about 25 parts of a voltatile solvent selected from the group consisting of petroleum hydrocarbon solvents, alcohols, ketones, lower chlorinated alkanes, aromatic hydrocarbons, and aliphatic ethers.

6. A fluid composition adapted to provide a protective coating for metals which contains as essential ingredients (A) from about to about parts of powdered zinc passing 325-mesh screen, (B) from about 14 to about 25 parts of an epoxy resin of 350-400 average molecular weight prepared by the reaction of 2,2-bis-(p-hydroxyphenyl) propane with epichlorohydrin, (C) from about 6 to about 10 parts of a zinc salt of the phosphorodithioic acid prepared by the reaction of a mixture of about equivalent amounts of isooctyl alcohol and dipropylene glycol with phosphorus pentasulfide (D) from about 8 to about 12 parts of an oil-soluble acylated amine prepared by mixing and heating at a temperature of from about 80 C. to about 200 C., a polyisobutene-substituted succinic anhydride wherein the polyisobutene has an average molecular weight of about 750 with about 4 equivalents of a mixture of diethylene triamine and triethylene, tetramine, and (E) from about 30 to about 70 parts of a volatile solvent consisting of a mixture of aromatic petroleum spirits and methyl isobutyl ketone.

References Cited by the Examiner UNITED STATES PATENTS 2,820,723 1/1958 Le Suer 117132 2,858,323 10/1958 Smith 260561 2,861,907 11/1958 Butler 260461.1l3 XR 2,970,972 2/1961 Wear et a1 260-47 XR 3,062,773 11/1962 Rogier 26018 3,075,932 1/1963 Edwards et al 26018 FOREIGN PATENTS 766,273 1/1957 Great Britain.

LEON J. BERCOVITZ, Primary Examiner. 

1. A FLUID COMPOSITION ADAPTED TO FORM A PROTECTIVE COATING ON METALS WHICH CONTAINS AS ESSENTIAL INGREDIENTS (A) FINELY DIVIDED ZINC, (B) AN EPOXY RESIN SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC-AROMATIC, ALIPHATIC, AND CYCLOALIPHATIC EPOXY RESINS, (C) A POLYVALENT METAL SALT OF THE PHOSPHORODITHIOIC ACID PREPARED BY THE REACTION OF A MIXTURE OF MONOHYDRIC AND POLYHYDRIC ALCOHOLS WITH A PHOSPHORUS SULFIDE, SAID POLYVALENT METAL BEING SELECTED FROM THE GROUP CONSISTING OF BARIUM, CALCIUM, STRONTIUM, MAGNESIUM, ZINC, CADMIUM, IRON, MANGANESE, LEAD, TIN, NICKEL, COBALT, CHROMIUM, AND BERYLLIUM, AND (D) AN OILSOLUBLE ACYLATED AMINE PREPARED BY MIXING AND HEATING AT A TEMPERATURE OF FROM ABOUT 80*C. TO ABOUT 200*C., A SUBSTITUTED SUCCINIC COMPOUND SELECTED FROM THE CLASS CONSISTING OF SUBSTITUTED SUCCINIC ACIDS HAVING THE STRUCTURAL FORMULA 